Growth and assimilation of NH4+ and NO3- by Paxillus involutus in association with Betula pendula and Picea abies as affected by substrate pH

H., Ek, S., Andersson, Kristina Arnebrant, Bengt Söderström

Research output: Contribution to journalArticlepeer-review

Abstract

The influence of pH on the growth and assimilation of N-15-labelled ammonium and nitrate was studied in intact ectomycorrhizal systems consisting of Betula pendula Roth and Picea abies (L.) Karst. colonized with a common mycelium of Paxillus involutus (Batsch) Fr. The plants were grown together in Plexiglass observation chambers containing non-sterile peat with three different pH values, 4.0, 5.1 and 6.1. The mycorrhizal mycelium was allowed to grow over a barrier into an area of peat from which plant roots were excluded. Labelled NH4NO3 was supplied, either as (NH4NO3)-N-15 or as (NH4NO3)-N-15, exclusively to the fungal mycelium. Shoots and roots were analyzed for N-15 in total nitrogen while the mycelium was analyzed for N-15 in NH4+, NO3- and free amino acids. The N-15 labelling pattern indicated that ammonium was immediately assimilated into amino acids, primarily glutamine, by the fungal mycelium at the uptake site. The amino acids were then translocated to the mycorrhizal roots. In contrast, nitrate-N was not assimilated in the mycelium but rather transferred to the mycorrhizal roots as nitrate. Mycelial uptake and transfer of N to the spruce and birch seedlings were significantly higher for NH4-N than for NO3-N. No firm conclusions about pH effects on the preferential uptake of ammonium and nitrate could be drawn. However, pH had a pronounced effect on the mycelial growth of P. involutus which was hampered severely at pH 6.1 and to a lesser extent at pH 5.1.
Original languageEnglish
Pages (from-to)629-637
JournalNew Phytologist
Volume128
Issue number4
DOIs
Publication statusPublished - 1994

Bibliographical note

The information about affiliations in this record was updated in December 2015.
The record was previously connected to the following departments: Lund University Libraries (016520000), MEMEG (432112240), Microbial Ecology (Closed 2011) (011008001)

Subject classification (UKÄ)

  • Biological Sciences
  • Ecology

Keywords

  • Mycorrhizas
  • ammonium
  • nitrate
  • amino acids
  • 16N

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